Thaw alarm

ABSTRACT

This invention relates to a thaw alarm which is operable to give a signal to indicate that thawing has occurred, or that the temperature in a particular environment, such as in a cold storage system, has risen to the melting point of water.

United States Patent Inventor Ralph L. Fenner Mill Valley, Calif. Appl. No. 834,089 Filed June 17, 1969 Patented Jan. 12, 1971 Assignee Hygrvnetrix, Inc.

THAW ALARM 9 Claims, 4 Drawing Figs.

U.S. Cl 200/6104, 337/300, 73/337 Int. Cl H0111 l/02 Field of Search 47/ (Inquired); 337/300, 326; 73/337, 337.5;

ZOO/61.04, 61.06

Primary ExaminerRobert K. Schaefer Assistant Examiner- M. Ginsburg Att0meyRobyn Wilcox ABSTRACT: This invention relates to a thaw alarm which is operable to give a signal to indicate that thawing has occurred, or that the temperature in a particular environment, such as in a cold storage system, has risen to the melting point of water.

PATENTEU m1 2|97| I NVENTOR.

Fig. 3

THAW ALARM The thaw alarm of the present invention preferably utilizes a bridled xeric element, such as the one described in connection with FIGS. 6 to 8, inclusive, of my copending application entitled Xeric Element and Method of Preparing the Same", filed on Jun. 17, 1969, Ser. No. 834,087. Such an element, as described in said application, is preferably the rib, or spine, of the seed-throwing arm which forms an extension of the seed pod of a seed-throwing plant, such as Geranium dissectum, Geranium Richardsonii, Geranium caespitosum, or Geranium eriostemon. After the seeds have matured and have been thrown, the seed pods are harvested, the throwing arms are retted for a period sufficient to loosen the soft fibrous material which covers a major portion of the rib, and the fibrous material is pulled away, as by passing the arm through the fleshy part of tightly compressed fingers of an operator. As described in my said application, the seed-throwing arm in its natural state assumes a flat spiral form extending through an arc of between 450 to 540, depending upon the dryness of the environment. When saturated with water, these ribs are straight and strong, and, when dry are-curved to form a spiral lying substantially in a single plane and extending through an arc of about 540, or one and one-half turns. In my preferred xeric element I take a length of 9 to 10 millimeters of such a rib for use as a moisture-sensitive member and place one or more (preferably three) such elements in a metallic saddle formed of a thin sheet of resilient metal, preferably of beryllium copper of a thickness of one one-thousandths of an inch. As a practical matter, I prefer to use a sheet of such material of a length of 14 millimeters and a width of 2 millimeters, the two ends of the strip being bent back upon a common face to form pockets at each end, each having a length of 2 millimeters leaving the overall length of the metallic element, or chip, at 10 millimeters. The fibers are placed in the saddle while they are thoroughly saturated and straight. The assembly is then quickly dipped at its ends in liquid solder in order to fill the ends of the pockets with fluid solder which, when it solidifies, fills the pocket and rigidly secures the ends of the fibers to the respective ends of the metallic saddle. At this point the chip, or combination of saddle and xeric elements, is perfectly straight, although it will bend to form an arc, the ends of which lie at an angle of about 60 with respect to each other if it is allowed to dry, assuming the form shown in FIG. 2 of this application. Immediately after the solder has solidified, and while the fibrous elements are still saturated, I quickly freeze the chip as by immersing in liquid nitrogen. This freezes the fibrous elements in their straight form which they will maintain as long as they remain frozen, even though the environment, such as a storage freezer, is normally sufficiently moisture free, to permit the fibrous elements to par tially dry and, therefore, bend the chip. The frozen chip so formed is placed in an electric circuit connected to a suitable alarm system, such as by forming a switch such as formed in FIG. 3. So long as the environment does not rise to a temperature which would permit the frozen xeric fibrous elements to thaw, i.e., the melting point of ice water, the switch maintains its open position. However, as soon as the environment reaches a temperature at which thawing occurs. The dryness of the environment causes the fibrous elements to dry, and bend the chip to close the switch as indicated in FIG. 4. Afier thawing, the device of the present invention would operate as a xeristatic switch, as described in my copending application entitled Xeristat", filed on Jun. 17, 1969, Ser. No. 834,088, but can be reconstituted as a thaw alarm switch by saturating the fibers with water so that they assume the straight form shown in FIGS. 1 and 3, and again freezing as above described.

OBJECTS It is a primary object of the present invention to provide a device which is normally irreversible to close a signal switch to indicate that an environment which is normally frozen below 32 F. has risen to that temperature, and which will maintain the switch closed until an operator manually opens the signal circuit to remove the switch, even though in the interim the environment has again reached a freezing temperature.

It is another object of the present invention to provide a device of the class described which is simple in construction, reliable in its operation, which has a long life, and which, although it may readily be reconstituted, is irreversible once it is indicated a thaw has occurred These and other objects of the invention will be apparent from the following detailed description of the device taken in conjunction with the accompanying drawings in which:

FIG. 1 is greatly enlarged perspective view of the chip, or bridled xeric element of the above-mentioned application,

showing its form when the moisture-sensitive fibers register saturation, or 100 percent relative humidity, or when such a chip has been frozen and kept in that condition.

FIG. 2 is a perspective view of the element of FIG. 1, shown.

FIG. 4 is a perspective view of the switch of FIG. 3 shown with the switch closed and indicative that a thaw has occurred.

In the preferred form of my invention I prefer to use a bridled" element of the type shown in FIGS. 6 to 8, inclusive, of my above-mentioned application for Xeric Element and Method of Preparing the Same". Such a xeric element has the fibrous moisture-sensitive members 10 attached to its supporting plate 25 only at its ends and hence is really only partially bridled thereto. However, in this art such elements are commonly referred to as being bridled as it is assumed that a fully bridled element (i.e., one in which the xeric element is attached to its plate throughout its entire length) will be so specified. The bridled element preferably comprises a saddle 25 formed of a thin resilient material, such as beryllium copper sheet with a thickness of one onefthousandths of an inch. I have found that a suitable size for practical applications of the invention uses a saddle formed of a sheet 25 of such material having a length of 14 millimeters and a width of 2 millimeters. Each end is bent back upon a common face to form opposing pockets 28 at the two ends of the chip, each tab 26 having a length of 2 millimeters. This leaves a chip, or saddle, having a pocket 28 at each end with an overall length of 10 millimeters and an overall width of 2 millimeters. The moisture-sensitive element 10 comprises the rib, or spine, of the throwing arm of the seed pod of a seed-throwing plant, such as Geranium dissectum, Geranium Richardsonii, Geranium caespitosum or Geranium eriostemon. The seed pods are harvested after the seeds have been thrown. Preferably, the throwing arms are removed from the remainder of the seed pod and these arms are soaked in warm water, preferably held to the temperature of the range from about to about F., for a period of about 3 weeks, or until the fibrous covering of the rib of the arm is readily separated from the rib by pulling the arm through 'tightly compressed fingers of an operator. A section of 9 millimeters in length is taken from these ribs 10 to be used in the bridled element. Since the ribs of the preferred plants are flat on one side and rounded on the other, it is a simple matter to place them flat on the chip 25, and if more than one element is used on the chip, to place all of them flat side against the chip so that the warp force of all of them work in the same direction. Preferably, three or four such elements are used, as I found that if this is done, they tend to equalize the small variations that may be found in individual elements, whereby calibration is rendered much simpler. In addition, I have found it desirable as a practical matter, to um material of a thickness sufficient to resist bending, such as using beryllium copper sheets of one onethousandths of an inch thickness, and to overcome this antibending characteristic of the metal by using a plurality of the fibrous elements so that as drying of the element occurs, the warp force of the drying elements readily bends the chip to the form shown in FIG. 2. The desired number of ribs it) are placed on the chip 25 with their fiat sides against the chip and their ends placed in their respective pockets 28. They are immediately dip soldered in melted solder to fill the pockets 2% with solder 27 and thus rigidly attach the ends of the respective fibers to the respective ends of the saddle 25. While the members are vegetable, and, therefore, can be burned, and do suffer an irreversible loss of effectiveness if heated to a temperature of above 125 C., the momentary dipping of the completely saturated fibers in the liquid solder does not harm them. The solder immediately cools and, therefore, rigidly attach the ends of the fibers to the saddle. The resultant chip or bridled element at this state continues to assume the form shown in FIG. 1 in which the saddle is perfectly straight. At this stage the chips are immediately quick frozen, as by dipping in liquid nitrogen. The frozen xeric elements 10 are frozen in the straight condition and cannot bend until they have been thawed. Thus, regardless of the dryness of the environment in which such a frozen chip may be maintained, it maintains the straight form shown in FIG. 1. Since these elements are designed to be used to signal a thaw in a frozen environment which normally is somewhat dry and would tend to bend an unfrozen chip, they can be used in a signal system in which they form one side of a bar switch.

If one end of the bridled element 25 is soldered to one wire 35 of an electric alarm circuit, it will form one contact of a bar switch. The other contact 35 is connected to the other wire 36 of such circuit, and so located as to engage the member 25 when that member has bent to a predetennined degree. Normally, these switches will be desired to operate, regardless of the humidity of the environment, so that the contact bar 35 will normally be placed quite close to the chip 25. it is obvious that when the environment in which the signal switch is located is below the freezing point of water, the frozen element 25'will maintain the straight position shown in MG. 3 and the switch will remain open. However, once the temperature rises above the freezing point of water, the fibrous ele ments likewise thaw, and then become true xeric elements in which they bend the chip 25 to an angle directly proportional to the relative humidity in the environment. Since the environment in which it is desired to operate these signal devices is not saturated, i.e., does not have a relative humidity of 100 percent, some bending effect will take place immediately upon thawing. Thus, the member 25 wiil bend toward the bar contact 35 and will soon engage that bar contact, thus closing the circuit. It is assumed that the electric circuit containing the leads 26 and 36 will control operation of some conventional signal device, such as ring a bell, light a signal lamp, or the like. Since such signal devices do not form a part of the present invention, they will not be described in detail.

However, it should be noted that once the arctic element." has thawed to permit movement to close the switch, reireerring of the environment will not open the switch, for if the fibers are again frozen, they will be frozen in the bent form. The thawed signal chip 25 can be reconstituted by dipping it in water until it is thoroughly saturated, and the chip assumes the form shown in FIG. 1, whereupon it is again quick frozen as by dipping in the liquid nitrogen. However, once the elements ltl have thawed so that they exert a warp force dependent upon the humidity of the environment they do not straighten from a change in temperature they respond only to the relative humidity of the environment in which they are placed.

it will be understood that the drawings and the above disclosure show a preferred embodiment of my invention and that many modifications will occur to those skilled in the art which will not depart from the inventive concepts herein disclosed. For example, it will be obvious to those skilled in the art that the chip of the present invention could be fully bridled in that it is attached to the chip throughout its entire length; or that the element would not form a part of the switch per se but its movement would be utilized by suitable linkage to close a separate switch. Accordingly, it IS intended that the claims cover such modifications as fall within the true spirit and concept of the invention.

1 claim:

1. A thaw signal device for use in a partially dry environment comprising: a saddle formed of a thin resilient metal, a moisture-sensitive fiber taken from the seed-throwing extension of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespetosum, and Geranium eriostemon, means rigidly securing the moisture sensitive fiber to the metallic saddle, said moisturesensitive fiber being straight and saturated with ice, means attaching one end of the saddle to one lead of a signal circuit, a contact engaged by the saddle in the event it moves a predetermined extent, and means attaching the contact to another lead of said signal circuit.

2. The device of claim 1 wherein the metallic sheet comprises beryllium copper with a thickness of approximately one one-thousandths of an inch.

3. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium dissectum.

4. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium Richardsonii.

5. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium caespitosum.

6. The device of claim l in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium eriostemon.

7. The device of claim 1 in which a plurality of moisturesensitive fibers are affixed to the metal plate.

8%. A thaw alarm for use in a partially dry environment comprising a switch adapted to be inserted in an electric circuit, said switch comprising: a xeric element comprising a saddle formed of a thin resilient metal, a. moisturesensitive fiber taken from the seed-throwing extension of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespitosum and Geranium eriostemon, said moisture mnsitive fiber being straight and saturated with ice, and means securing the frozen fiber to the metallic saddle, and means including said xeric element for opening and closing said switch.

9. The device of claim l in which the moisture-sensitive fiber is attached to the metallic saddle at its ends only. 

1. A thaw signal device for use in a partially dry environment comprising: a saddle formed of a thin resilient metal, a moisture-sensitive fiber taken from the seed-throwing extension of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespetosum, and Geranium eriostemon, means rigidly securing the moisture sensitive fiber to the metallic saddle, said moisture-sensitive fiber being straight and saturated with ice, means attaching one end of the saddle to one lead of a signal circuit, a contact engaged by the saddle in the event it moves a predetermined extent, and means attaching the contact to another lead of said signal circuit.
 2. The device of claim 1 wherein the metallic sheet comprises beryllium copper with a thickness of approximately one one-thousandths of an inch.
 3. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium dissectum.
 4. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium Richardsonii.
 5. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium caespitosum.
 6. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed-throwing arm of the seed pod of the plant Geranium eriostemon.
 7. The device of claim 1 in which a plurality of moisture-sensitive fibers are affixed to the metal plate.
 8. A thaw alarm for use in a partially dry environment comprising a switch adapted to be inserted in an electric circuit, said switch comprising: a xeric element comprising a saddle formed of a thin resilient metAl, a moisture-sensitive fiber taken from the seed-throwing extension of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespitosum and Geranium eriostemon, said moisture sensitive fiber being straight and saturated with ice, and means securing the frozen fiber to the metallic saddle, and means including said xeric element for opening and closing said switch.
 9. The device of claim 1 in which the moisture-sensitive fiber is attached to the metallic saddle at its ends only. 